Optical image scanners are widely used for generating digital representations of real-world objects, particularly media such as documents which may include text, graphics, printed images, and the like. With flatbed scanners, media is maintained in a fixed position on a platen during scanning by a moveable scan bar. Alternatively, with document scanners (also called sheet-fed scanners), the media is fed past a fixed-position scan bar during scanning. In order to generate digital representations having high image quality, calibration of the scanner may be desirable. For some scan bar technologies, re-running the calibration may be desirable in order to ensure high image quality over time.